The invention relates to a lithography system for writing a pattern on a moveable target, such as a wafer, and a storage system for storing data comprising a measured position of the target within the system. The invention further relates to a method for storing such positional data.
United States patent application 2011/0029685 describes a method and system in which data recording the operation of an exposure apparatus is output via a communication path to an information processing apparatus comprising a storage unit for storing said data, and a communication unit for transmitting data requested by one or more terminals to said one or more terminals. This data recording the operation of the exposure apparatus may comprise information measured by a wafer stage measurement system for use by a wafer stage control system to control the position of a wafer, and may be stored for weeks or days to be requested at a later time through one of the terminals for further analysis.
In similar systems, the storage unit forms part of a feedback control loop, which feedback control loop comprises one or more sensors for sensing a position of a target in an exposure apparatus, wherein said sensed positions are stored in the storage unit, an actuator for moving said target within the exposure apparatus, and a control unit for controlling the actuator to move the target within the exposure apparatus based on the measured positions stored in said storage unit.
A drawback of these known systems is that the storage unit, in order for it to be able to keep up with the supply of data, must be able process data at least at the same rate as the wafer stage measurement system. This is prohibitively expensive when the amount of positional data to be recorded is very large, especially when the data is being stored in and read out from the storage system at substantially the same time.
It is an object of the present invention to provide a lithography system and method providing a more cost effective way for storing positional data of a target.